Log in with your ASH credentials. Click on Einstellungen (gear icon) in the upper right corner:

You can change the language via the Bereich – Benutzeroberfläche (Section - user interface) menu, in this example to English:

To set up forwarding, click on Forwarding in the menu on the left:

Select the Redirect to option off in the upper dropdown menu and enter the desired email address in the input field:

Set the lower dropdown menu to On to activate the forwarding. Confirm with Save: